Novel Quantitative Electroluminescence Method for Detailed Performance Analysis of PID-s Affected Crystalline Silicon PV Module

Potential induced degradation shunting (PID-s) is a rapid degradation mode, which severely affects the performance and lifetime of a photovoltaic (PV) module. Electroluminescence imaging is generally used to investigate PID-s; however, mainly, its use has only been limited to qualitative work. In this article, the novel quantitative electroluminescence (QUEL) method is proposed for the detailed performance evaluation of a PID-s affected module. The effects of PID-s progression on the fundamental PV cell characteristics are analyzed. More emphasis is given to a cell current-electroluminescence (EL) intensity (
I
_EL
-φ
_EL
) characteristic as it enables the extraction of individual cell information within a module. Analysis reveals, a nonlinearity in
I
_EL
-φ
_EL
characteristic solely reflects the effect of shunting. The degree of nonlinearity depends on the nature and severity of PID-s. Whereas PID-s insignificantly affects cell voltage-EL intensity characteristic. Based on this analysis, the two stage QUEL method is developed; it requires a minimum four EL images, a module datasheet, and EL measurements. In the first stage, the QUEL algorithm extracts seven parameters of an individual PV cell mainly by decoding a cell
I
_EL
-
φ
_EL
curve. The second stage involves two diode model based simulations of an individual cell and module, which generates
I-V
curves at desired operating conditions. The proposed method was experimentally validated with 10 individual cells and modules. Results show that the QUEL method estimates cell or module power with <±3% relative error. Also, generated
I-V
overlaps well with an experimental
I-V
curve and enables detailed cell level quantitative analysis of shunting defects and degradation.